This is Eckels. Eckels is on his way to the time machine place to go back in time, to when dinosaurs were around.
On the way
Stay on the path. Don't go off
Eckels is at the time machine place. And he is ready to go back in time a shoot a dinosaur. But some unsuspecting rules come up for Eckels that makes him a little nervous
I can't do this
Don't shoot until I say
Eckels is in the time machine with his guide. The guide is now telling him some rules that he must follow. He is not allowed to walk off the path, and he is not allowed to kill anything unless the guide says he can. And if he disobeys these rules, it will mess up the future.
Back to the "future"
Eckels is on the right path to the dinosaur. He's a little nervous but ready to fight it. But something unsuspecting happens to Eckels
Eckels sees the size of the dinosaur and gets nervous, and second thoughts. So he turns around and runs, but as he's running he goes off the path and steps on a butterfly. Which cause problems in the future.
When Eckels got back into the future. He noticed some things just were not right. He looked around and behold right in front of him a butterfly drops dead. later on he sees this sign with all its letters mixed up. Eckels gets scared and all worried that he wrecked the future, with only killing one butterfly.